Z-Axis will only go down...

[benway]

Hey All,

I moved my machine to a new shop months ago and haven't been able to use it for a while. Went to start it today and it all boots as usual, but upon hitting the "Home" button I get that horrible sound that means a motor is at the end of its travel and still going.
I realized then that the Z-Axis was somehow already at the bottom of it's travel and ramming although it should have been going up vs down. I always store it homed and ready and don't think it creeped down on it's own while being stored.
It's very possible that it was pushed down so that it could fit through a doorway.

So, I hit cancel and restarted. Tried instead moving each axis on its own with the controller.
X and Y both move as normal, but Z would only move down, regardless of pressing the Up button.
No issues with slow/fast speeds however, and nothing appears bent, loose or unplugged.
I turned it fully off, unplugged it, and manually returned the spindle to the top position of the Z-Axis with no more than the normal resistance that doing this exerts.
Went all on, tried homing again and it technically worked since the Z-Axis was already at the top, but upon trying the up/down buttons it will still only advance down, toward the bed.

I have an earlier AR8 Pro machine. I have never had any issues with the steppers, or the controller except for ones I've created through accidents and even still it has never functioned improperly.
My manual says "Revised 3 August 2015" on the front, and I'm pretty sure I bought it at the end of 2015 (new from Axiom). I have the original controller Axiom packaged these with, but am fuzzy on the details.

Any thoughts, reset methods or things I may have glossed over while looking for a similar problem?

Thanks,
Ben

[aluomala]

Did you check the z-axis coupler (under the cover)? If it's broken or loose, it might only travel in the one direction.

Allan

[benway]

I checked under the plastic cover that sits atop the Z-Axis and both connections are firmly seated. No wires appear to be questionable or pulled out either.
Is that the cover you're referencing?

Thanks, Allan!

[gerry]

Do you watch the coupler when you try to move the Z? Draw a line on the upper shaft, coupler and lower connection. They should still be aligned after the move.

[benway]

Hey Gerry,

Thanks for the reply.
Not sure I follow though.
I do understand the method you're prescribing though and use it when moving things that I know I'll need to re-align later.
I have not loosened/tightened the motor>coupler>ballscrew for any reason yet either, but I do know the hex screws within are all tight still.

The Z stepper turns in the same direction when pressing either the up or down button on the controller.
There's no question that it's moving, or that the standard moves (tiny incremental steps vs faster continuous moves) are also exactly the same as the moves made by the other axes.
It's not loose/drifting when off or anything like that either. It just won't got back up electronically.
The only way I can currently return the Z to the top/zero point is manually when the machine is off.